This application is related, generally and in various embodiments, to a multi-layer printed circuit board. For applications requiring increased device densities, it is well known in the art to use multi-layer printed circuit boards to minimize the footprint required by the printed circuit board. As the area allotted for the footprint decreases, the spacing between components decreases and the difficulty of meeting various isolation requirements becomes more difficult. For many circuit board layouts designed to meet the space and isolation requirements, the layouts often experience undesired hot spots and termination losses that lead to premature board failure.
Examples of such layouts are shown in FIGS. 1A-D and 2A-E. FIGS. 1A-D illustrate an exploded view of layers of a multi-layer printed circuit board 10. The printed circuit board 10 includes a first layer 12, a second layer 14, a third layer 16, and a fourth layer 18. The printed circuit board 10 also includes a first via 20, a second via 22, and a third via 24. The printed circuit board 10 further includes a first winding 26 and defines an opening 28. The opening 28 is configured to receive a magnetic core therein.
Referring to FIG. 1A, a first turn of the first winding 26 starts at the lower left portion of the first layer 12, winds around the opening 28 in a counter-clockwise direction, and connects to the first via 20, which extends from the first layer 12 to the second layer 14. As shown in FIG. 1A, the first winding 26 is arranged to maintain a certain minimum distance from the opening 28. The first winding 26 is also arranged to maintain a certain minimum distance from the second via 22 and to maintain a certain minimum distance from the third via 24. Due to limitations of the packaging area available on the first layer 12, the cross-sectional area of the first winding 26 is noticeably reduced proximate the second via 22 to maintain the desired minimum distance between the first winding 26 and the second via 22 and noticeably reduced proximate the third via 24 to maintain the desired minimum distance between the first winding 26 and the third via 24.
Referring to FIG. 1B, a second turn of the first winding 26 arranged on the second layer 14 starts at the first via 20, winds around the opening 28 in a counter-clockwise direction, and connects to the second via 22, which extends from the second layer 14 to the third layer 16. As shown in FIG. 1B, the first winding 26 is arranged to maintain a certain minimum distance from the opening 28. The first winding 26 is also arranged to maintain a certain minimum distance from the third via 24. Due to limitations of the packaging area available on the second layer 14, the cross-sectional area of the first winding 26 is noticeably reduced proximate the third via 24 to maintain the desired minimum distance between the first winding 26 and the third via 24.
Referring to FIG. 1C, a third turn of the first winding 26 arranged on the third layer 16 starts at the second via 22, winds around the opening 28 in counter-clockwise direction, and connects to the third via 24, which extends from the third layer 16 to the fourth layer 18. As shown in FIG. 1C, the first winding 26 is arranged to maintain a certain minimum distance from the opening 28. The first winding 26 is also arranged to maintain a certain minimum distance from the first via 20. Due to limitations of the packaging area available on the third layer 16, the cross-sectional area of the first winding 26 is noticeably reduced proximate the first via 20 to maintain the desired minimum distance between the first winding 26 and the first via 20.
Referring to FIG. 1D, a fourth turn of the first winding 26 arranged on the fourth layer 18 starts at the third via 24, winds around the opening 28 in a counter-clockwise direction, and ends at the lower left edge of the fourth layer 18. As shown in FIG. 1D, the first winding 26 is arranged to maintain a certain minimum distance from the opening 28. The first winding 26 is also arranged to maintain a certain minimum distance from the first via 20 and to maintain a certain minimum distance from the second via 22. Due to limitations of the packaging area available on the fourth layer 18, the cross-sectional area of the first winding 26 is noticeably reduced proximate the first via 20 to maintain the desired minimum distance between the first winding 26 and the first via 20 and noticeably reduced proximate the second via 22 to maintain the desired minimum distance between the first winding 26 and the second via 22.
The reduction or necking down of the cross-sectional area of the first winding 26 proximate the first via 20, the second via 22, or the third via 24 can easily result in undesirable hot spots and termination losses that lead to premature failure.
FIGS. 2A-2E illustrate an exploded view of layers a multi-layer printed circuit board 30. The printed circuit board 30 is similar to the printed circuit board 10, but also includes a fifth layer 32 and a second winding 34 arranged on the fifth layer 32. Referring to FIG. 2E, the terminations of the second winding 32 are located at the lower right portion of the fifth layer 32. Similar to the first winding 26, the second winding 34 is arranged to maintain a certain minimum distance from the opening 28. The second winding 34 is also arranged to maintain a certain minimum distance from the first via 20 and to maintain a certain minimum distance from the third via 24. Due to limitations of the packaging area available on the fifth layer 32, the cross-sectional area of the second winding 34 is noticeably reduced proximate the first via 20 to maintain the desired minimum distance between the second winding 34 and the first via 20 and noticeably reduced proximate the third via 24 to maintain the desired minimum distance between the second winding 34 and the third via 24. The reduction or necking down of the cross-sectional area of the second winding 34 proximate the first via 20 or the third via 24 can also easily result in undesirable hot spots and termination losses that lead to premature failure.